Disclaimer: What you're about to read is some very technical, very geeky stuff, but don't panic if you don't have your kinesiology degree just yet. In the future articles in this series, Eric and Mike will break it all down for you and show you how to fix your posture and improve your physique. For now, take off that poseur trucker hat and put on your thinking cap!

Do the Evolution, Baby

Evolution is defined as "a process in which something passes by degrees to a more advanced or mature stage." Think back to prehistoric times and try to envision your ancestors. You probably have an image conjured up of a Neanderthal wearing a loincloth, grunting at females, killing his own food, and hunching over a fire to stay warm. His DNA endured century after century, guaranteeing that you're equally hardcore, right?

Then again, you wear boxer briefs, utter cheesy pickup lines at every woman you see, hunt for your food at the local Stop 'N Shop, and hunch over a computer all day. In other words, the only trait you share with this prehistoric badass is your pathetic S-shaped posture: rounded shoulders, forward head posture, exaggerated kyphosis, anterior pelvic tilt, excessive lordosis, internally rotated femurs, and externally rotated, flat feet.

Well, it's time to once and for all dissociate yourself from the Neanderthals by correcting these structural problems. We're here to help you do just that. This four-part series will outline the most common postural distortions and provide a comprehensive program to correct them.

The Length-Tension Relationship

First, let's talk about muscular contraction. You've heard of the sliding filament theory, right? No? You’re not a total kinesiology geek like us, huh? Well, here's a brief synopsis:

Actin and myosin filaments are found within the sarcomere (a contractile unit of skeletal muscle). The myosin cross bridges attach to the actin filaments, pulling them inward and leading to an overall shortening of the muscle fiber. When a bunch of fibers do this at once, we get a concentric muscle action (contraction or shortening).

With the sliding filament theory in mind, you can imagine that changes in the length of a muscle fiber can affect the ability of the muscle to contract optimally. For example, when a sarcomere is too short, it can't generate peak force because of the preexisting overlap of actin filaments. This overlap takes up valuable space that could otherwise be used for the myosin cross bridges to attach. Conversely, when the sarcomere is excessively lengthened, the actin filaments are too spread out for all of the myosin cross bridges to reach them for attachment.

So, we know that a muscle fiber (and, in turn, the entire muscle) is strongest when the sarcomeres are at their ideal resting length (usually resting position or slightly more lengthened). In all other positions, the sarcomere is outside of this ideal length zone and can't generate maximal force. Just consider how your strength varies in certain portions of the barbell curl and you'll understand what we mean.

Posture and the Length-Tension Relationship

The length-tension relationship isn't only important at the cellular level; training — or lack thereof — can alter a muscle's normal resting length. Simply put, the more you train a muscle, the shorter it wants to get.

Meanwhile, the response of the antagonist is to lengthen more and more over time to allow the agonist to shorten. If you need a visual, wrap an elastic band around your wrist. Pull on one side to loosen it (the antagonist) and note that the other side tightens (the agonist). This is how concentric muscle actions normally occur; the antagonist must relax to permit the agonist to shorten.

The problem herein lies when the agonists become chronically shortened due to poor training and/or lifestyle behaviors. Summarily, we get shortened (hypertonic or overactive) muscles and lengthened (hypotonic or inhibited) muscles opposing each another. Now, toss the length-tension considerations into the mix; do you think muscles (and their individual fibers) that are always outside of the optimal length zone will be able to generate maximal force? Is the Pope Hindu?

When discussing length and tension, you must also be aware that they're not one and the same. A muscle can have excellent length but still be excessively tight and vice versa (although it’s not as common). It's generally accepted that with length, more is better unless you have the flexibility of a circus sideshow freak. Muscle length is usually improved via stretching (static, dynamic, PNF, etc.)

On the flip side, tension is more of a bell-shaped curve. On one hand, excessive tension is problematic as stated above, but excessive laxity isn’t beneficial either. Tension is a true tight rope and something that should be evaluated frequently. Tension is best improved using modalities like massage, heat, muscle stim, or myofascial release.

The Caveman Look

It's time to apply the aforementioned principles to your caveman posture. Essentially, with the classic S-shaped posture, you have overactive and inhibited muscles from head to toe. The origin of such distortion is unique to each case. In some cases, these problems result from developmental or congenital structural abnormalities such as rearfoot or forefoot varus, Scheuermann's disease, or spondylolisthesis (just to name a few).

However, these cases aren't the norms when it comes to screwy posture; rather, the Neanderthal look is usually a function of poor postural habits and improperly balanced training focus at multiple joints. Therefore, in weight-training populations without actual structural irregularities (read: you!), the most beneficial corrective programs will work to resolve the problem at each affected joint. Beginning with the core (a common source of postural problems), here's a depiction of how several joints interact in this common postural distortion:

• The core and glutes are inhibited; the hip flexors, hamstrings and erector spinae are overactive. This results in anterior pelvic tilt and exaggerated lordosis (swayback).

(Image from Medline Plus)

• There's a natural kyphosis to the thoracic spine. If the spine continued in the lordosis direction, our chests would be facing the ceiling all the time. Kyphosis is a means of keeping us upright in spite of the lordosis occurring below. In other words, there's a direct relationship between lordosis and kyphosis: when one increases, so does the other (in order to maintain upright posture). Remember that while lordosis and kyphosis are natural, it’s only when they come to excess that things get ugly.

• Also worthy of note is the fact that the latissimus dorsi origin is on the lowest six thoracic vertebrae, lumbar vertebrae, sacrum, and ilium (the last three via the thoraco-lumbar fascia), providing a direct muscular link between the upper (humerus) and lower body. Likewise, the erector spinae group has broad attachments on the pelvis, ribs, vertebrae, and skull, allowing it to exert profound effects on both upper and lower body posture, and the link between the two.

• Weakness of the core is also implicated in that it essentially allows the torso to descend and its mass to move anteriorly (or forward). As this occurs, the scapula moves up and outward (wing) around the rib cage, the clavicle is pressed to the first rib, the humerus internally rotates, and the head comes forward so that the body can continue to function in this modified position.

• Just as a continuation of excessive lordosis is impractical, continuation of kyphosis direction to the cervical vertebrae would have you looking at the floor all the time! As such, when kyphosis is excessive, the posterior neck muscles must be constantly active in order to pull the back of the head posteriorly (thus bringing the chin up) to compensate for the neck moving forward. Just think of someone hunched over a computer (like you're doing right now!) and you'll see what we mean.

• Moving on to the lower body, there are definite anterior pelvic tilt implications on the femur. Specifically, anterior tilt of the pelvis forces the femur into internal rotation. This places stress on the lateral part of the thigh, most notably the vastus lateralis muscle and the tensor fascia latae (TFL) and iliotibial band (ITB). These areas become shortened, tight, and are usually implicated in cases of lateral knee pain.

• While the inward rotation of the femurs carry on to the tibiae, it's important to note that a condition known as genu valgum (knock knees) often develops. With this condition, the tibia abducts (moves away from the midline of the body) relative to the femur. This can place a great deal of stress on the medial aspect of the knee.

The tibia internally rotates on the talus in the closed-chain position. This internal tibia rotation is associated with pronation of the subtalar joint (involves the talus and calcaneus). In plain English, this means your feet flatten.

• Human movement — especially squatting — requires a certain amount of dorsiflexion. The pronated foot scenario is related to tightness of the plantarflexors (calves); the individual pronates the foot to overcome/avoid a compromised range of motion in dorsiflexion.

• Trainees can also compensate for this lack of dorsiflexion by externally rotating the feet. As a result, there's usually shortening of the lateral leg musculature and lengthening/inhibition of the anterior leg musculature in the lower extremity. The proximal and distal tibiae positions give the image of a valgus or knock-knee appearance of the entire leg complex.

Now, this only refers to static posture. Just imagine what happens when someone with these postural afflictions actually tries to move around! Several injuries and/or conditions may result from each postural flaw:

Potential kyphosis/rounded shoulders manifestations: bicipital tendonitis, injuries to the glenoid labrum, subacromial impingement and resulting rotator cuff tears, injuries to teres major, scapular winging, decreased thoracic outlet space, degeneration of vertebral facets/acromioclavicular joints/sternoclavicular joints, and various elbow pathologies (due to compensatory overload).

Potential head forward posture manifestations: headaches, excessive dry mouth (over-reliance on breathing through the mouth), difficulty swallowing, anterior and posterior neck tightness, and irritation along the medial scapular border.

Potential lower body manifestations: low back pain, disc injuries, sciatica/radiating pain from the low back into the legs/feet, decreased low body power and strength production, lateral knee pain, medial collateral ligament tears/sprains, anterior cruciate ligament tears/sprains, excessive pronation of the foot (flat feet), ankle sprains, hamstring/lower back strains, sacroiliac joint dysfunction, piriformis syndrome, pain in the forefoot (metatarsalgia), bunions, and plantar fasciitis. Oh yeah, let's not forget the ever-popular incontinence.

Numerous muscles cross these joints and all of the actions of each muscle will be affected by alterations to optimal resting length. To give you an idea of how dramatic an effect these subtle distortions can have on every exercise you perform, consider the following muscles that may be affected and their functions:

Upper Body: Hypertonic/Shortened/Overactive

1. Pectoralis Major: glenohumeral extension (sternal fibers only), flexion (clavicular fibers only), horizontal adduction, internal rotation, adduction (sternal only, when below 90° of abduction), and abduction (clavicular only, after 90° abduction or more).

2. Latissimus Dorsi: glenohumeral extension, adduction, internal rotation, and horizontal abduction; scapular depression, retraction, downward rotation, and posterior tilt.

3. Teres Major: glenohumeral extension, internal rotation, and adduction.

4. Anterior Deltoid: glenohumeral abduction, flexion, horizontal adduction, and internal rotation.

5. Subscapularis: glenohumeral internal rotation, adduction, extension, and stabilization.

6. Upper Trapezius: scapular elevation, upward rotation, and retraction (in certain positions); head/neck extension.

7. Levator Scapulae: scapular elevation (duh), retraction, downward rotation, and anterior tilt.

8. Sternocleidomastoid: head/neck flexion, contralateral rotation, ipsilateral flexion.

9. Pectoralis Minor: scapular protraction, downward rotation, depression, and anterior tilt.

10. The Suboccipitals (Rectus Capitis Posterior Major, Rectus Capitis Posterior Minor, Obliquus capitis inferior, and Obliquus capitis superior): head/neck extension and ipsilateral flexion and/or rotation.

Note: The temporalis and masseter (facial muscles) also become overactive with forward head posture, as they must constantly contract in order to keep the mouth closed from this position (tension in the hyoid muscles of the neck forces the mandible posteriorly and inferiorly).

Upper Body: Hypotonic/Lengthened/Inhibited

1. Rhomboid Major and Minor: scapular retraction, downward rotation, and elevation (barely noticeable; this movement occurs during retraction).

2. Infraspinatus and Teres Minor: glenohumeral external rotation, horizontal abduction, extension, and stabilization.

3. Middle Trapezius: scapular elevation, retraction, and upward rotation.

4. Lower Trapezius: scapular depression, retraction, upward rotation, and posterior tilt.

5. Neck Flexors (Longus Coli, Longus Capitus): cervical flexion, ipsilateral flexion and rotation.

6. Posterior Deltoid: glenohumeral horizontal abduction, extension, abduction, and external rotation.

7. Serratus Anterior: scapular protraction, upward rotation, and posterior tilt.

8. Cervical and Thoracic erectors (Semispinalis, Spinalis, Longissimus, and Iliocostalis: Cervicis and Thoracis fibers): cervical and thoracic extension, ipsilateral flexion and rotation.

Lower Body: Hypertonic/Shortened/Overactive

1. Iliacus, Psoas Major and Minor, Rectus Femoris: hip flexion and external rotation.

2. Rectus Femoris: hip flexion and knee extension.

3. Lumbar Erector Spinae (Spinalis, Longissimus, and Iliocostalis: Lumborum fibers): hip extension and lateral flexion of spine.

4. Quadratus Lumborum: ipsilateral flexion and stabilization of pelvis and lumbar spine. However, when active bilaterally, the QL contributes to lumbar extension, which can be accentuated with anterior pelvic tilt.

5. Hamstrings (semitendinosus, semimembranosus, biceps femoris): hip extension, internal rotation (semitendinosus and semimembranosus), and external rotation (biceps femoris only); knee flexion, internal rotation (semitendinosus and semimembranosus), and external rotation (biceps femoris only).

6. TFL/ITB (ITB is fascia): hip abduction, flexion, and internal rotation.

7. Adductors (Adductor Longus, Brevis, and Magnus; Gracilis, and Pectineus): hip adduction, flexion or extension (depending on position), and external or internal rotation (depending on position), and knee flexion (gracilis only).

8. Piriformis, Gemellus superior, Obturator Internus, Gemellus Inferior, Obturator Externus, and Quadratus Femoris: hip external rotation.

9. Vastus lateralis: knee extension

10. Peroneals (Peroneus longus, brevis, and tertius): eversion, plantarflexion (tertius contributes to dorsiflexion).

11. Soleus: plantarflexion

12. Gastrocnemius (especially lateral head): plantarflexion, knee flexion.

Lower Body: Hypotonic/Lengthened/Inhibited

1. Gluteus maximus: hip extension, external rotation, and adduction (lower fibers only).

2. Gluteus medius and minimus: hip abduction, internal rotation (both), and external rotation (medius only as the hip abducts).

3. Rectus Abdominus: lumbar flexion and ipsilateral flexion.

4. Transverse Abdominus (TVA): stabilization of lower back (function is integrated with multifidus and pelvic floor muscles).

5. Multifidus (lumbar): segmental spinal stabilization (synergist of TVA), lumbar extension, and rotation (both contralateral and ipsilateral).

5. Internal Oblique: lumbar flexion, ipsilateral flexion, and ipsilateral rotation.

6. External Oblique: lumbar flexion, ipsilateral flexion, and contralateral rotation.

7. Vastus medialis: knee extension

8. Tibialis anterior: inversion and dorsiflexion

9. Tibialis posterior: inversion and plantarflexion

Your Homework Assignment

And you thought poor posture wouldn’t affect your training! In Part II, we'll highlight several postural assessments and functional tests you can perform to give yourself a better idea of your structural flaws.

In the meantime, your homework assignment for the next week is to have someone take full body (head to toe) pictures of your normal standing posture from both sides and the front and back (preferably in just your underwear).

Don't chicken out! You absolutely have to take pictures of yourself to get an idea of how you stand (pun intended). You can also do this in front of a mirror, but it’s usually less effective because you'll want to fix your posture or subconsciously try to improve it. Moreover, it’s damn hard to take photos of your own back! Anyway, be sure to get those photos taken so that we can hit the ground running next week!

About the Authors

Eric Cressey, BS, CSCS is currently pursuing a Master's Degree in Kinesiology with a concentration in Exercise Science at the University of Connecticut. He graduated from the University of New England with a double major in Exercise Science and Sports and Fitness Management. Eric has experience in athletic performance, rehabilitation, and general conditioning settings. He can be contacted at ericcressey@hotmail.com.

Mike Robertson, M.S., C.S.C.S., U.S.A.W., is the Director of the Athletic Performance Center (APC) in Fort Wayne, Indiana. The APC offers sport performance training, injury rehabilitation, and personal training services to its clients. Mike received his Masters in Sports Biomechanics from the Human Performance Lab at Ball State University. Mike has been a competitive powerlifter for the last three years and is currently the USA Powerlifting State Chair in Indiana. To contact Mike, please send an email to mikerob022@yahoo.com.

References

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2. Floyd, R.T., & Thompson, C.W. Manual of Structural Kinesiology. McGraw Hill, 2001.

3. Smith, L.K., Weiss, E.L., & Lehmkuhl, L.D. Brunnstrom's Clinical Kinesiology: 5^th Edition. F.A. Davis Company, 1996.

4. Tiberio, D. Pathomechanics of structural foot deformities. J Am Phys Ther Assoc. 1988 Dec;68:1840-49.